1. Field of the Invention
The present invention relates to techniques for performing oilfield operations relating to subterranean formations having reservoirs therein. More particularly, the invention relates to techniques for performing oilfield operations involving an analysis of oilfield conditions, such as geological, geophysical and reservoir engineering characteristics, and their impact on such operations.
2. Background of the Related Art
Oilfield operations, such as surveying, drilling, wireline testing, completions, production, planning and oilfield analysis, are typically performed to locate and gather valuable downhole fluids. Various aspects of the oilfield and its related operations are shown in FIGS. 1A-1D. As shown in FIG. 1A, surveys are often performed using acquisition methodologies, such as seismic scanners or surveyors to generate maps of underground formations. These formations are often analyzed to determine the presence of subterranean assets, such as valuable fluids or minerals. This information is used to assess the underground formations and locate the formations containing the desired subterranean assets. This information may also be used to determine whether the formations have characteristics suitable for storing fluids. Data collected from the acquisition methodologies may be evaluated and analyzed to determine whether such valuable assets are present, and if they are reasonably accessible.
As shown in FIGS. 1B-1D, one or more wellsites may be positioned along the underground formations to gather valuable fluids from the subterranean reservoirs. The wellsites are provided with tools capable of locating and removing hydrocarbons, such as oil or gas, from the subterranean reservoirs. As shown in FIG. 1B, drilling tools are typically deployed from the oil and gas rigs and advanced into the earth along a path to locate reservoirs containing the valuable downhole assets. Fluid, such as drilling mud or other drilling fluids, is pumped down the wellbore through the drilling tool and out the drilling bit. The drilling fluid flows through the annulus between the drilling tool and the wellbore and out the surface, carrying away earth loosened during drilling. The drilling fluids return the earth to the surface, and seals the wall of the wellbore to prevent fluid in the surrounding earth from entering the wellbore and causing a ‘blow out.’
During the drilling operation, the drilling tool may perform downhole measurements to investigate downhole conditions. The drilling tool may be used to take core samples of the subsurface formations. In some cases, as shown in FIG. 1C, the drilling tool is removed and a wireline tool is deployed into the wellbore to perform additional downhole testing, such as logging or sampling. Steel casing may be run into the well to a desired depth and cemented into place along the wellbore wall. Drilling may be continued until the desired total depth is reached.
After the drilling operation is complete, the well may then be prepared for production. As shown in FIG. 1D, wellbore completions equipment is deployed into the wellbore to complete the well in preparation for the production of fluid therethrough. Fluid is then allowed to flow from downhole reservoirs, into the wellbore and to the surface. Production facilities are positioned at surface locations to collect the hydrocarbons from the wellsite(s). Fluid drawn from the subterranean reservoir(s) passes to the production facilities via transport mechanisms, such as tubing. Various equipments may be positioned about the oilfield to monitor oilfield parameters, to manipulate the oilfield operations and/or to separate and direct fluids from the wells. Surface equipment and completion equipment may also be used to inject fluids into reservoirs, either for storage or at strategic points to enhance production of the reservoir.
During the oilfield operations, data is typically collected for analysis and/or monitoring of the oilfield operations. Such data may include, for example, subterranean formation, equipment, historical and/or other data. Data concerning the subterranean formation is collected using a variety of sources. Such formation data may be static or dynamic. Static data relates to, for example, formation structure and geological stratigraphy that define geological structures of the subterranean formation. Dynamic data relates to, for example, fluids flowing through the geologic structures of the subterranean formation over time. Such static and/or dynamic data may be collected to learn more about the formations and the valuable assets contained therein.
Sources used to collect static data may be seismic tools, such as a seismic truck that sends compression waves into the earth as shown in FIG. 1A. Signals from these waves are processed and interpreted to characterize changes in the anisotropic and/or elastic properties, such as velocity and density, of the geological formation at various depths. This information may be used to generate basic structural maps of the subterranean formation. Other static measurements may be gathered using downhole measurements, such as core sampling and well logging techniques. Core samples are used to take physical specimens of the formation at various depths as shown in FIG. 1B. Well logging involves deployment of a downhole tool into the wellbore to collect various downhole measurements, such as density, resistivity, etc., at various depths. Such well logging may be performed using, for example, the drilling tool of FIG. 1B and/or the wireline tool of FIG. 1C. Once the well is formed and completed, fluid flows to the surface using production tubing and other completion equipment as shown in FIG. 1D. As fluid passes to the surface, various dynamic measurements, such as fluid flow rates, pressure and composition may be monitored. These parameters may be used to determine various characteristics of the subterranean formation.
Sensors may be positioned about the oilfield to collect data relating to various oilfield operations. For example, sensors in the drilling equipment may monitor drilling conditions, sensors in the wellbore may monitor fluid composition, sensors located along the flow path may monitor flow rates and sensors at the processing facility may monitor fluids collected. Other sensors may be provided to monitor downhole, surface, equipment or other conditions. Such conditions may relate to the type of equipment at the wellsite, the operating setup, formation parameters or other variables of the oilfield. The monitored data is often used to make decisions at various locations of the oilfield at various times. Data collected by these sensors may be further analyzed and processed. Data may be collected and used for current or future operations. When used for future operations at the same or other locations, such data may sometimes be referred to as historical data.
The data may be used to predict downhole conditions, and make decisions concerning oilfield operations. Such decisions may involve well planning, well targeting, well completions, operating levels, production rates and other operations and/or operating parameters. Often this information is used to determine when to drill new wells, re-complete existing wells or alter wellbore production. Oilfield conditions, such as geological, geophysical and reservoir engineering characteristics, may have an impact on oilfield operations, such as risk analysis, economic valuation, and mechanical considerations for the production of subsurface reservoirs.
Data from one or more wellbores may be analyzed to plan or predict various outcomes at a given wellbore. In some cases, the data from neighboring wellbores, or wellbores with similar conditions or equipment may be used to predict how a well will perform. There are usually a large number of variables and large quantities of data to consider in analyzing oilfield operations. It is, therefore, often useful to model the behavior of the oilfield operation to determine a desired course of action. During the ongoing operations, the operating parameters may need adjustment as oilfield conditions change and new information is received.
Techniques have been developed to model the behavior of geological formations, downhole reservoirs, wellbores, surface facilities as well as other portions of the oilfield operation. Examples of these modeling techniques are shown in Patent/Publication/Application Nos. U.S. Pat. No. 5,992,519, WO2004/049216, WO1999/064896, U.S. Pat. No. 6,313,837, US2003/0216897, U.S. Pat. No. 7,248,259, US2005/0149307 and US2006/0197759. Typically, existing modeling techniques have been used to analyze only specific portions of the oilfield operations. More recently, attempts have been made to use more than one model in analyzing certain oilfield operations. See, for example, Patent/Publication/Application Nos. U.S. Pat. No. 6,980,940, WO2004/049216, US2004/0220846 and Ser. No. 10/586,283. Additionally, techniques for modeling certain aspects of an oilfield have been developed, such as OPENWORKS™ with, e.g., SEISWORKS™, STRATWORKST™, GEOPROBE™ or ARIES™ by LANDMARK™; VOXELGEO™, GEOLOG™ and STRATIMAGIC™ by PARADIGM™; JEWELSUITE™ by JOA™; RMS™ products by ROXAR™, and PETREL™ by SCHLUMBERGER™.
Despite the development and advancement of various aspects of oilfield analysis, there remains a need to provide techniques capable of performing a complex analysis of oilfield operations based on a wide variety of parameters affecting such operations. It is desirable that such a complex analysis provide a unified view of selective portions of the oilfield operation, such as geological, geophysical, reservoir engineering, drilling, production engineering, economic and/or other aspects of the oilfield. This unified view may be used to view, analyze and/or understand the co-dependencies of the individual portion(s) of the oilfield operations and the interaction therebetween. Such a system would preferably permit consideration of a wider variety and/or quantity of data affecting the oilfield to generate a common understanding of current and/or future conditions of the oilfield by selectively connecting desired modules throughout the oilfield. Preferably, the provided techniques would be capable of one of more of the following, among others: calibrating measurements from different scales (methods of measurement and volume of influence for such measurements), efficiently analyzing data from a wide variety of sources, generating static models based on any known measurements, selectively modeling based on a variety of inputs, selectively simulating according to dynamic inputs, adjusting models based on probabilities, selectively connecting models of a variety of functions (e.g. economic risk and viability), selectively performing feedback loops throughout the process, selectively storing and/or replaying various portions of the process, selectively displaying and/or visualizing outputs (e.g. displays, reports, etc.), selectively updating the models as new measurements become available, providing the ability to numerically simulate static and dynamic properties, providing the ability to perform economic analysis throughout the modeling system, selectively performing desired modeling (e.g. uncertainty modeling), providing workflow knowledge capture, enabling scenario planning and testing, providing reserves reporting with associated audit trail reporting, dynamically connecting selective models in an application and generating a surface model from selected oilfield modules.